Electrical system.



H. GROB.

ELECTRICAL SYSTEM.

APPLICATION FILED mun. m1.

1 ,256,223. Patented Feb.12,1918.

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APPLICATION FILED JAN. 30. mil.

1,256,223. v Patented Feb. 12,1918.

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AAAAA AA H H nnminmk l VENTOR 2 ATTORNEYS UNITED STATES PATENT OFFICE.

HUGO (mos, or ZURICH, SWITZERLAND, assrenon T0 SAFETY can HEATING &

LIGHTING comrm, A CORPORATION or NEW JERSEY.

ELECTRICAL SYSTEM.

Patented Feb. 12, 1918.

Application filed January 30, 1911. Serial No. 605,629.

To all whom it may concern:

Be it known that I, HUoo Gnon, a citizen of Switzerland, and residing at Zurich, Switzerland, have invented certain new and useful Improvements in Electrical Systems, of which the following is a full, clear, and exact description.

This invention relates to an electrical system, and with regard to certain more specific features, to the electric lighting of railwa trains or other vehicles.

no object of the invention is to provide a ractical and eilicient system for maintaining constant the voltage of a translation circult.

Another object is to provide reliable means for the regulation of the voltage of a circuit where the source of power is a dynamo subject to wide variations of speed.

Another object is to provide a system of the above general nature in which the loadvoltage is held substantially constant regardless of variations in the load-current.

Another object is to provide a simple and effective system enabling a variable-speed generator to charge a storage-battery and at the same time to maintain a constant voltage across'a translation circuit.

Another object is the provision of a system wherein two storage-batteries may be simultaneously charged at different rates of current flow and yet both be available to supply the load automatically when necesplication of which will be indicated in the following claims. 7 g

In the accompanyin drawings, wherein are shown diagrammatically one or more of various possible embodiments of the several features of my invent on,

Fi 3'shows an embodiment in which adivislon of the generator voltage is obtained by means of two separate armature windings; and a Figs. 4 and oshow the system illustrated in Fig. 4, with additional features Similar reference characters refer to similar parts throughout the different views of the drawings.

Referring now to these drawings in do tail, Fig. 1 shows conventionally a generator with its field-current derived from a separately excited exciter. At 1 and 2 are illnstrated two points, such as terminals of the mains to the translation devices 3, between which it is desired to maintain a constant voltage. A low-resistance excitation winding 4 is mounted on the exciter. The current .for this excitation winding 4 is obtained through leads 5, 6, connected to a source of power at the terminals 7, 8.

At 9 is illustrated a current-controlling device which possesses the roperty of entirely or substantially thrott ing the current I passing through it, when the impressed voltage (that is, the voltage across the device due to the connections between that device and the rest of the apparatus, not any electro-motive force that may be inherent in the device itself) is below a certain critical limit, and of offering but slight resistance to an external current whose voltage impressed on the device 9 is above the said critical limit, so that a slight increase of the impressed voltage above the said limit will be sufiicient to cause a considerable amount of current to pass through the device 9. The device 9 may take the form of a galvanic battery, a mercury arc lamp, an electrolytic cell, or other similar apparatus. A galvanic battery, as is well known, allows practically no current to be passed through it unless the impressed voltage is greater than the electro-motive force of the battery itself, in

which case the battery ofi'ers but little resistance to the passage of this current. Men

cury arc lamps and electrolytic cells act in and by the conductor 11 with the point 2.-

T he other terminal of the exciting winding 4 is connnected to the point 1. A resistance 12 is provided between the points 7, 8 and the exciting coil 4, for the purpose of keeping the current passing through the conductors 5, 6 fairly constant regardless of variations in the current in the shunt 10-91121. If the voltage across the terminals 7, 8 is not substantially constant,

' then resistance 12 should be of iron, to limit the current passing through the conductors 5, 6 to a predetermined value regardless of fluctuations in the voltage across the terminals 7, 8.

The current flowing through the excitation coil 4 will obviously be affected by the net electrical opposition (due to electrical resistance, galvanic or dynamic electro-motive force, electro-motive force of polarization, and any other electrical properties) offered by the shunt 109l121 around said coil. If the device 9 has an electromotive force of its own, as a storage-battery, it is so designed that with the proper generator voltage this clectro-motive force, added algebraically to the voltage 1, 2 will almost equal the resistance of the exciting coil 4, multiplied by the current normally in the conductors 5, 6, with the result that almost all the current in the conductors 5,

6 passes through the coil 4, and only a little of it through the shunt 10-91121. If the device 9 has no electro-motive force of its own, as a mercury vapor lamp, then its electrical opposition (With the voltage 1, 2 not excessive) is large enough to eii'ect the same result, namely, that almost all the current in the conductors 5, 6 passes through the coil 4. In either case as soon as the generator voltage, which in Fig. 1 is equal to the voltage 1, 2, rises above its proper value, the net electrical opposition of the shunt 1091121 decreases and more of the current in the conductors 5, 6 is thereby diverted through this shunt. leaving a Sllillll current passing through the coil 4. This-reduces the excitation of the generator. The generator voltage is thus maintained at a value just high enough to It is, of course, important that the elec-- trical opposition offered by the device 9 be .as constant as possible, and independent of the magnitude and duration of the current- 7 sent through it. If the device/9 takes the form of a cell with an electrolyte, some wellknown electrolyte-stirring apparatus (not shown in'the drawings) may be used for this purpose. V

In Fig. 2 the exciting coil 4 is on'the enerator itself, and not on the exciter. Ot erwise" the system illustrated in this figure operates in the same way as Fig. 1.

In the succeeding figures the exciting coil 4 is illustrated as applied to the generator itself; but it is to be understood that this coil may equally well be instead a part of an exciting dynamo for the generator.

The source of electricity provided between the points 7, 8 may be supplied by the main generator itself, but not from the i terminals 1, 2, because the voltage across the points 7, 8 must be of oppositepolarity to that across the terminals 1, 52. This effect may be attained by having the voltage 1, 2 equal to only a part of the total generator voltage, the rest of the generator voltage being employed acrcss 7, 8. This division of the generator voltage may be effected by utilizing separate armature windings, as illustrated in Figs. 3, 4 and 5. In the preferred method of dividing the generator voltage, shown in Figs. 3, 4 and 5, the armature conductors are divided into two groups, insulated from each other and each having a commutator; the commutators are provided with brushes 1, 2 and 7, 8, respectively. The connection between brushes 1 and 7 results in a series connection between the brushes 1, 2 and 7, 8.

The current-controlling device 9 may consist of a storage-battery, and in case the battery should be required for storage purposes. it would be desirable to provide for quickly recharging it. Since the conductors 5, 6 de.iver only a little more current than the maximum current required by the exciting coil 4, the current flowing normally in the shunt 10-9-11-21 would not be sufficient to charge the battery 9 rapidly. However, the greater voltage across the points 2. 8 (Figs. 3. 4 and 5) mav be ad antagecusly emploved as illustrated in Figs.

4 and 5 for charg ng a batterv 14, wh ch is changed for this latter battery from time to time by means hereinafter described. In order to avoid an excessive charging current to the battery 14, a current-limiting device, such as an iron resistance 15, may be provided in the charging circuit. This arrangement illustrated in Figs. 4 and 5 may be used with advantage in connection with plants for the electric lighting, heating or ventilating of railway carriages. In plants of this description, it is often desirable to recharge the battery 14 more uickly when the load is on. ThlS may be e ected by arranging a resistance 16 between the brush 1 and the junction of the conductor to the translating devices 3 and that to the exciting winding 4, as illustrated in Figs. 4 and 5. In this case it will be necessary for the generator to generate a sufiicient excess of voltage to compensate for the voltage drop across the resistance 16; this excess of voltage, which is substantially proportional to the load, will enable the battery 14- to be charged at a higher rate when the load is on.

The means for exchanging the connections to the two batteries from time to time may take any approved form. I have shown in Fig. 5 a device set forth in detail in my Patent, No. 994,510 granted June 6, 1911, as an illustration of switching mechanism useful in an electrical system on railway cars or other vehicles. At 17 is illustrated a centrifugal governor, adapted to be driven by the motion of the vehicle and to rotate the ratchet wheel 18 one-quarter 01 a revolution each time the speed of the governor rises above or falls below a predetermined limit. The quarter-revolutions of the ratchet wheel 18 move the switch 19 from the lower or upper position to the central position, or vice versa, as the case may be, and simultaneously operate the switch 20, so as to connect the generator to the translation circuit and the batteries 9, 14 alternatively across the brushes 1, 8 each time the generator speed rises above the critical limit, and to connect the batteries 9, 14 in parallel across the translation circuit and disconnect the generator from said circuit whenever the generator speed drops below this limit.

In Figs. 3, 4 and 5 the battery 9 is being continually charged with a small current, equal to the difference between the current passing through the winding 4 and that passing through the conductors 5, 6. As a result of this continual char ing, the counter electro-motive force of tie battery and with it the voltage of the whole system will increase with the increase in the extent to which the battery is charged. In order to protect the translatin devices 3 from too high a voltage, it is a visable to provide an automatic cut-out device 21 to interrupt the current in the conductors 5, 6 as soon as the voltage of the translation circuit has reached acertain maximum. It will be noted from Fig. 4 that when this circuit is opened by the device 21, the excitation of the generator is then proportional to the difference in potential between brushes 1, 2 and battery 9, as is the case in my Patent No. 994,510, above mentioned. This results in the slow discharge of the battery 9. The same is true of Fig. 5.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shail be interpreted as illustrative and not in limiting sense. I It is also to be understood, that the Iangua e used in the following claii is inten ed to cover all. of the generic and speeific features of the invention herein described and all statements oi the 1e the invention, which, as a matter or ian gua e, might be said to fail therebetween.

aving described my invention, what I claim as new and desire to secure by Letters Patent is: p 1. In an electrical system, in combination, a variable-speed generator, a device which substantially prevents the passage through itself of current at an im 'essed voltage of less than a predetermined value, means adapted to influence the excitation of the generator, means for delivering a substantial] constant current to the terminals of said rstmeans, terminals having a voltage substantially proportional to the total induced voltage of the generator, and a shunt around said first terminals, said shunt including said device and said second terminals.

2. In an electrical system, in combination, a variable speed generator, a device which substantially prevents the passage through itselfof current at an impressed voltage of less than a predetermined value, two armature windings on said generator, means adapted to influence the excitation of said generator, a circuit including one of said windings, said means and a resistance, said resistance being adapted to maintain the current through said circuit substantially constant, and a shunt circuit around said means and including said device and the other of said windings.

3. In an electrical system, in combination, a variable speed generator, a device which substantially prevents the passage through itself of current at an impressed voltage of less than a predetermined value, means adapted to influence the excitation of the generator, circuit connections between said device and said means, said means being re-, sgonsive to an increase of current forced t rough said device to reduce the excitation of said generator, a work circuit containing translating devices, a storage battery adapted to be charged by said generator, and means for automatically rendering said first means inoperative when the voltage. at 1 the translating devices exceeds a predetermined limit.

In testimony whereof I afiix my signature in the presence of two witnesses.

HUGO GROB. Witnesses:

HENRY HASPER, Wonomnm HAUr'r. 

